When fiber fleeces are produced, fiber flocks are first dispensed from a fiber flock feeder to a transport device, which, in a first alternative, transports them in the form of a fiber flock mat to a fiber web-forming device, preferably a carding machine. In a second alternative, they are transported directly to an aerodynamic fleece former; or, in a third alternative, the fiber flocks are transported directly to a solidification machine such as a needling machine.
In the first alternative, the carded web formed in the fiber web-forming device (which can also be called a single-layer or double-layer fleece) is then sent to a fleece layer, which lays the fiber web to form a multi-layer fleece by cross-lapping. This multi-layer fleece can then be solidified by a suitable solidification machine such as by a needling machine. Overall, the goal is usually to produce a fiber fleece with a very high degree of uniformity. For this purpose, appropriate means of intervening in the process are present at various locations of the production system. For example, in the area between the fiber flock feeder and the web-forming device, the weight, for example, of the fiber flock mat can be measured by a belt weigher, and on this basis the infeed rate of the web-forming device is controlled in such a way that the quantity of fiber material which arrives in the web-forming device per unit time is always the same.
Nevertheless, a belt weigher of this type can determine only the average weight of the fiber flock mat distributed across the width of the transport device and over a certain length in the transport direction. For this reason, the uniformity of the fiber flock stream entering the web-forming device obtained by this equalizing method is only roughly approximate. The mass per unit area of the fiber flock mat can thus vary across the width of the fiber flock mat, a situation which must be tolerated.
In the case of the second and third fleece-forming alternatives mentioned above, attempts have been made in the past through various adjustments within the processing stations and through various design details to dispense the fiber flocks in the fiber flock feeder to form a fiber flock mat and to deliver the individualized fibers in the aerodynamic fleece-forming machine to form a fiber fleece as uniformly as possible over the length and width of the fiber flock mat or fleece. The results, however, have often been in need of improvement.
In addition to making a uniform fiber flock mat or fleece, it can also be advantageous in other cases for the transverse profile and/or longitudinal profile of the fiber flock mat or the fleece to comprise a predetermined type of nonuniformity.